Following enrollment of the initial 3 arms; additional cohorts of 20 patients for intermediate cohorts (not to exceed 2.0 mg/kg) may be added at the time of dose escalation up to 1.0 mg/kg and up to 2.0 mg/kg (eg, 0.75 mg/kg or 1.5 mg/kg respectively) based on assessment by the Steering Committee of available safety and efficacy data when at least six subjects have at least three cycles of treatment in the current dose level.